1. Field of the Invention
The present invention relates generally to a high frequency integrated circuit used in a portable wireless communication device, and relates more particularly to a multimode wireless transmitter affording low power consumption in a smaller and lighter device, and to a portable wireless device using said multimode wireless transmitter.
2. Description of Related Art
Mobile communication devices increasingly feature functions affording compatibility with different communication systems, and multiband systems that operate across multiple frequency bands are becoming more common. Wireless devices compatible with such systems are extremely complex, necessitate large scale circuits, and have multiple oscillators that can result in spurious errors. See, for example, Japanese Unexamined Patent Application 2000-13274.
Conventional dual-mode portable communication terminals that operate on two frequency bands have two completely separate transmission channels with the RF sections tuned to separate frequencies and sharing few parts. Reducing the size, weight, and power consumption is therefore extremely difficult.
The present invention is directed to solving the foregoing problems of the prior art, and an object of the invention is to provide a multimode wireless transmitter affording a reduction in size, weight, and power consumption by using a common orthogonal modulator and amplifier in the transmission channels of a dual-mode portable communication terminal that operates on two frequency bands, providing a switch at the amplifier output to selectively supply signals to the transmission circuits in the different modes, and controlling changing the operating mode of the oscillator and two frequency dividers by means of a switch. A further object of the invention is to provide a portable wireless device using this multimode wireless transmitter.